Fire Extinguisher Size Recommendations

Selecting the appropriate size and type of fire extinguisher is crucial for ensuring effective fire suppression and workplace safety. This document outlines the recommended sizes for fire extinguishers based on specific fire hazards and occupancy types, drawing from established safety standards and best practices.

General Requirements

Employers are responsible for providing and maintaining appropriate firefighting equipment, including portable fire extinguishers, suitable for the potential fire hazards in their facilities. There should be no delay in providing necessary equipment as fire hazards occur. Defective equipment must be replaced immediately. [1] [1]

All portable fire extinguishers must bear an approved label from a nationally recognized testing laboratory. [1]

Fire extinguishers should be readily accessible along normal paths of travel in the protected area and their locations clearly indicated, even if visual obstructions are present. [1] [2]

Classification of Fires and Extinguisher Types

Fire extinguishers are selected and distributed based on the classes of anticipated workplace fires. Different classes of fires require different types of extinguishing agents: [7]

Class A: Fires involving ordinary combustible materials like wood, cloth, paper, rubber, and many plastics. Extinguishers suitable for Class A fires include water, foam, loaded stream, or multipurpose dry chemical.
Class B: Fires involving flammable liquids, gases, or greases. Suitable extinguishers include Halon 1301, Halon 1211, carbon dioxide, dry chemicals, foam, or loaded stream.
Class C: Fires involving energized electrical equipment. Extinguishers for Class C fires include Halon 1301, Halon 1211, carbon dioxide, or dry chemical. It is crucial that the extinguishing agent is nonconductive.
Class D: Fires involving combustible metals such as magnesium, titanium, zirconium, sodium, or potassium. These fires require specific dry powder extinguishing agents approved for use on the particular metal.
Class K: Fires involving combustible vegetable or animal oils and fats, typically found in commercial kitchens. Class K extinguishers are specifically designed for these types of fires.

[9] [6] [9] [6] [9] [6] [9] [7] Specific Size and Placement Recommendations

Class A Fires:

A fire extinguisher with a rating of not less than 2A should be provided for each 3,000 square feet of protected building area, or major fraction thereof. The travel distance from any point in the protected area to the nearest fire extinguisher should not exceed 75 feet. [8] [8] [1]

In multistory buildings, at least one fire extinguisher rated not less than 2A should be located adjacent to the stairway on each floor. [1] [8] [5]

A 1/2 inch or larger interior diameter garden hose that is not more than 100 feet in length and that is equipped with a nozzle may be substituted for a 2A fire extinguisher if it is capable of reaching all points in the area that would be covered by the replaced extinguisher and is capable of discharging not less than 5 gallons per minute with a horizontal hose stream of not less than 30 feet. The hose line shall be mounted on a rack or reel. Not more than 1/2 of the total number of required fire extinguishers may be replaced by the hose. [1]

Class B Fires:

A fire extinguisher rated not less than 10B should be provided within 50 feet of locations where more than 5 gallons of flammable or combustible liquids or 5 pounds of flammable gas are being used on the job site. This requirement does not apply to the integral fuel tanks of motor vehicles. [3] [5] [8]

Class K Fires:

A Class "K" extinguisher should be maintained within 30 feet of hazards where there is a potential for fires involving combustible vegetable or animal oils and fats. [2] [7]

Specific Locations:

Outside of, but not more than 10 feet from, a door opening to a room used for the storage of more than 60 gallons of flammable liquids, a portable fire extinguisher that has a rating of not less than 20 BC units shall be located.
Not less than 25 feet, nor more than 75 feet, from an outside storage area, a portable fire extinguisher that has a rating of not less than 20 BC units shall be located.
On each tank truck or other vehicle used to transport or dispense flammable liquids, a portable fire extinguisher that has a rating of not less than 20 BC units shall be located.
Each service or fueling area shall have at least 1 portable fire extinguisher which has not less than a 20 BC unit rating and which is located within 75 feet of each pump, dispenser, underground fill opening, and lubricating or service area.
Storage locations for liquefied petroleum gas (L.P.G.) shall be provided with at least 1 approved portable fire extinguisher that has a rating of not less than 20 BC.
Each site of a hazardous process shall be provided with a portable fire extinguisher of an appropriate size and type.

[3] [3] [3] [3] [3] [3] Occupancy Type Considerations

Light Hazard Occupancies:

In light hazard occupancies, where the amount of combustibles or flammable liquids present is such that fires of small size may be expected (e.g., offices, schoolrooms, churches), smaller extinguishers may suffice, provided they meet the area coverage and travel distance requirements. [9]

Ordinary Hazard Occupancies:

In ordinary hazard occupancies, where fires of moderate size may be expected (e.g., mercantile storage and display, auto showrooms, light manufacturing), extinguishers with higher ratings and capacities are necessary to address the increased fire load. [9]

Extra Hazard Occupancies:

In extra hazard occupancies, where fires of severe magnitude may be expected (e.g., woodworking, auto repair, aircraft servicing), extinguishers with the highest ratings and capacities, or fixed fire equipment systems, are essential. [9]

Alternative Fire Suppression Methods

In some cases, standpipe systems or hose stations connected to a sprinkler system can be used instead of Class A portable fire extinguishers, provided that such systems meet specific requirements and employees are trained in their use. Up to 100 feet of 1 1/2-inch hose with a nozzle capable of discharging water at 25 gallons or more per minute may be substituted for a fire extinguisher rated not more than 2A in the designated area, provided that the hose line can reach all points in the area. [7] [4]

Inspection, Maintenance, and Training

Portable fire extinguishers must be visually inspected monthly to ensure they are fully charged and operable. Extinguishers should be maintained in a fully charged and operable condition and kept in their designated places at all times except during use. [10] [7] [10]

A tag should be attached to each extinguisher showing the dates of inspection, recharging or servicing, the name of the servicing agency, and the name of the person who did the service. [10]

Employers must provide training to employees on the use of portable fire extinguishers, including the proper selection, operation, and limitations of extinguishers. Employees should also be informed of evacuation procedures and emergency phone numbers. [1]

Conclusion

Selecting the correct size and type of fire extinguisher, combined with proper placement, inspection, maintenance, and employee training, is essential for maintaining a safe workplace and ensuring effective fire suppression. Compliance with relevant safety standards and regulations is crucial for protecting lives and property.